NEW YORK (Reuters) - The world's leading treatments for
hepatitis C were similarly effective in the first large trial
pitting them against each other, Schering-Plough Corp said on
Monday.

The company said its Pegintron injectable drug and Roche
Holding AG's better-selling Pegasys drug both cut the liver
damaging virus to undetectable levels in roughly 40 percent of
patients.

Schering-Plough also said a lower-dose formulation of its
injectable Pegintron was as effective as the standard dose of
Pegintron. But the lower-dose formulation caused a similar
incidence of side effects as the standard dose of Pegintron,
possibly undercutting any potential marketing advantages.

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Both drugs are used in combination with an antiviral pill
called ribavirin and are considered the standards of care.

Schering-Plough, which devised the head-to-head trial after
U.S. sales of Roche's newer medicine leapfrogged Pegintron,
declined to predict whether results of the study would help
Pegintron reclaim lost market share.

The trial involved 3,070 patients infected with the
genotype 1 strain of hepatitis C, the most common but
hardest-to-treat form of the virus. An estimated 4 million
Americans are believed to be infected with hepatitis C, the
leading cause of liver transplants.

None of the patients in the so-called IDEAL trial had
previously been treated for the infection.

They were divided into three groups, including one that
received standard 1.5 microgram weekly doses of Pegintron plus
ribavirin and one that received a 1 microgram weekly dose of
Pegintron plus ribavirin. That smaller dose of Pegintron is
sold by Schering-Plough but used by a relatively small number
of patients who take it as a stand-alone treatment.

Another group in the trial received the standard 180
microgram weekly dose of Pegasys plus ribavirin.

After 48 weeks of treatment and then 6 months of
observation, no detectable sign of the virus was found in 41
percent of patients taking Pegasys, in 40 percent of those
taking standard doses of Pegintron and in 38 percent of those
taking low-dose Pegintron.

"Efficacy in all three groups was similar, with about 40
percent of patients achieving a sustained virologic response,"
Consalvo said.

"The overall incidence of adverse events for the three
regimens were similar," Consalvo said, as were the numbers of
patients who dropped out of the trial due to side effects that
included flu-like symptoms, fatigue and anemia.

Consalvo said 24 percent of patients taking standard doses
of Pegintron experienced relapses, meaning a return of
detectable viral infection, after the 48-week treatment period.
That was similar to the 20-percent relapse rate among the
low-dose Pegintron group.

Although the relapse rate was higher for the Pegasys group,
at 32 percent, the percentage of Pegasys patients having no
detectable virus levels in the final analysis was similar to
the two Pegintron groups.

"The lower relapse rate for the Pegintron patients was
meaningful clinically," Consalvo said, but was not deemed
statistically significant.

Shares of Schering-Plough were down 6.7 percent to $25.87
in early afternoon trading, which analysts attributed to
concern about mixed results from a separate trial involving the
company's Vytorin cholesterol fighter.